Huasheng 142f problems

I have a a brand new huasheng 142f and it's completely stock besides the gas tank. I had to remove the stock one because it was rusty on the inside which clogged the carburetor. I replaced the tank with a pit bike tank. I cleaned the carburetor with carb cleaner and put it back on. After that I tested the bike and it started. I got on and started twisting the throttle. It pulled but it felt like I was only going less than 10mph. If I went full throttle it wouldn't go any faster and it would die. But I would be able to start it again. What should I do?